One of Earth's defining features is its magnetic field. It forms a protective shield against high-energy particles ejected by the Sun and thus arguably has provided life with a safer place to grow into the complex array of organisms we see today.
The most stunning indications of Earth's magnetic field are auroras, dancing curtains of colorful light that appear near the North and South poles during times of high solar activity. Another sign that Earth has a magnetic field is that a compass points north wherever you are on the planet.
